bug#25987: 25.2; support gcc fixit notes

[Eli Zaretskii]

> Cc: 25987@debbugs.gnu.org, tom@tromey.com
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 9 Mar 2017 19:37:45 +0200
> 
> On 09.03.2017 18:56, Eli Zaretskii wrote:
> 
> > It sounds gross to ask people to use Flymake just to be able to use
> > something like this.
> 
> What's gross about that?

It's a large package, and its purpose is not just fix compilation
errors.